I'm trying to convert a .mkv file file to .avi, I used Super to convert and it did successfully. The problem is that the original file (.mkv) have two audio streams (dual audio), and when I convert it to .avi, Super "takes" only one audio stream but I want both.

I do not mean to offend you at all by saying this so don't get all bent out of shape as this is NOT directed at you, but Super is intended to be used by idiots. The fact that you posted here at all means you're above its intended audience. You'll probably need to find a guide on Xvid4PSP, but it should easily be able to do what you want.

I do not mean to offend you at all by saying this so don't get all bent out of shape as this is NOT directed at you, but Super is intended to be used by idiots.

If it's intended to be "used by idiots," why does it have such a convoluted GUI?
Actually, I'd recommend against SUPER, these days, primarily due to the malware/spyware concerns, and that there are easier tools out there to work with.

cbble: As far as I recall (since I haven't bothered with SUPER in quite some time), there's no way to specify which audio track you want to work with in a multiple audio-track video. It'll be easier to extract the audio tracks, as Baldrick mentioned, with something like MKVCleaver or gMKVExtractGUI (both are more recently updated than MKVExtractGUI-2), then pick which one you want and add it when you're converting the video in SUPER, or whatever converter you're using.